The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cce7668a987c08d515f8ab0d7996d4ea40d6d2de

commit cce7668a987c08d515f8ab0d7996d4ea40d6d2de
Author: Jennifer Apacible <apacible@chromium.org>
Date: Sat Mar 31 21:57:39 2018

[Picture in Picture] Hide video playback in tab behind interstitial.

Currently, video playback is visible behind the Picture in Picture
interstitial while in PIP mode. Ideally, only the video poster image,
icon, and text of the interstitial should be visible.

This change follows the pattern used for Media Remoting to disable
seeing video playback in the browser tab while in PIP/MR mode.

BUG:  826588 
Change-Id: I1d3ba9978e0c68cfbed59618e82123a8cad876f6
Reviewed-on: https://chromium-review.googlesource.com/983055
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547390}
[modify] https://crrev.com/cce7668a987c08d515f8ab0d7996d4ea40d6d2de/third_party/WebKit/Source/core/html/media/PictureInPictureInterstitial.cpp

+hbengali for fyi, should be fixed in next canary

@apacible: Could you please provide us with a sample test cases & URL of the issue which would help us to verify the issue further from TE end.

Thanks in Advance.